The straight, or vertical, bow has been around since the time man began to hunt for food or to defend himself. Some say the vertical bow transitioned into the recurve crossbow design as early as 400 BC. In fact the Chinese adapted the crossbow for warfare by 204BC and had as many as 50,000 crossbowmen in their ranks. The early crossbows of the recurve type were quite heavy and lacked the range and accuracy of the traditional straight or recurve bow. As time passed the design of crossbows rendered them lighter and more accurate crossbow with scope.
More recently, the compound crossbow has gained popular use in large part due to its relative ease of cocking and its increased power potential. The compound crossbow has a system of pulleys around which the string, or cable, must be strung and attached to each end of the prod or lath. This pulley system, just noted above, results in significant mechanical advantage in cocking and added power at the moment the arrow is released. Both the recurve and compound crossbows have their fervent advocates. It really boils down to ones own preference based upon either experience or perceived advantage or both.
The crossbow is a relatively simple design. It is basically a simple stock, not unlike a rifle stock, upon which is securely attached a “prod” (sometimes referred to as a “lath”). The prod or lath is a wood (usually a laminate) or a metal arm with a string or cable attached to each end of the prod. When the string is drawn back the prod bends and stores energy until the arrow (or bolt) is launched by releasing the drawn back string. The stiffer or more rigid the prod, the more difficult it is to draw the string back but the higher the stored energy and the higher the resulting launch velocity.